Conventionally, in image forming apparatuses such as MFPs that perform image forming process based on a plurality of types of functions such as a copy function, a printer function, and a facsimile function, a configuration is adopted in which, when work has continuously not been performed for a predetermined time, it is possible to execute a power-saving mode in which the power consumption during standby is decreased by cutting off the power supply to each portion of the device. Specifically, in an image forming apparatus that performs electrophotographic image forming process, the control temperature of a fixing device, which has a comparatively high power consumption, is switched to a temperature lower than the melting temperature of toner during the power-saving mode. Accordingly, when executing the power-saving mode, it is not possible to immediately begin the next image forming process, and image forming process is begun after waiting for completion of a return processing that raises the temperature of the fixing device to the toner melting temperature.
Here, among the image forming process based on the plurality of types of executable functions in an image forming apparatus such as an MFP,
in the image forming process of an ordinary print function or fax function, each image forming process request is independently generated, user operation of the image forming apparatus before the start of processing is not made necessary, and so it is not necessary for the user to go to the installation location of the image forming apparatus. Accordingly, even when switching to the power-saving mode immediately after the image forming process of the printer function or the fax function has been completed, the convenience of the user is not impaired.
However, when performing image forming process in which user operation of the image forming apparatus is necessary before starting processing, such as the image forming process of the copy function, it is possible to intermittently perform a plurality of image forming processing that sandwiches operation of the device by a single user such as setting of copy conditions and document exchange. Thus, when the time after the image forming process is complete until switching is made to the power-saving mode is short, it is necessary to wait for completion of the return processing whenever starting the next image forming process.
In consideration of such points, image forming apparatuses have been proposed in which the switching time, which is the time from completion of the image forming process until switching to the power-saving mode, is determined according to the type of the function in the immediately previous image forming process and the connection status of the host device (see patent documents 1 and 2).
However, in conventional image forming apparatuses in which the switching time is determined according to the function of the image forming process that was executed immediately before, when a plurality of different types of image forming process are executed in parallel, or when a plurality of different types of image forming process have been generated in tandem, there is the problem that the determined switching time is not a logical amount of time, leading to a decrease in the user's convenience and work efficiency.
For example, when fax transmission data or print data is received during image forming process of the copy function for a plurality of document sets and image forming process has been executed for data received at the point in time that image forming process of the copy function for a single set of documents was completed, the final image forming process becomes image forming process of the facsimile function or the printer function, and while the user is performing operation of the device such as preparation of a document set for the next image forming process of the copy function or operation to set copy conditions, the device switches to the power-saving mode in a comparatively short amount of time after the time that image forming process of the received data is completed, and it is possible that without being able to perform the next image forming process of the copy function immediately at the point in time that the user completed operation of the device, the user will be unable to smoothly perform image forming process of the copy function for a plurality of document sets.
It is an object of this invention to provide an image forming apparatus in which it is possible to realize effective power-saving without impairing the convenience of the user, by determining the timing for switching to a power-saving mode based on historical information of, for example, image forming process or operation related to image forming process.    Patent document 1: JP 2000-184106A    Patent document 2: JP 2000-151863A